SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21ec9f34326fb528ccb6c6a77e2d0356430291d85f75fbb1bc9ad1925f867c50' 
  AND token = 'eF9s79Rr5djhU+mABIE/DGwNC22uVwnZvpmyP5QqmVQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}